Compacted conformal antenna at lower-UWB for wireless capsule endoscope system

A compact sized ingestible antenna is presented at 3.3 GHz for lower ultra-wide band (UWB) wireless capsule endoscope system, by taking the stomach part of human body model presence into consideration. The proposed novel design is based on microstrip feed model and consists of three unique strip lines at center, The tuning of strip lines length and gaps between them achieved the intended frequency band of operation. This unique design helped in reducing the size of the antenna significantly and can maintain the operational band in flexible condition which proves advantage while integrating the antenna inside the capsule. The dimension of the antenna excluding the superstrate are 5.4 mm × 7 mm × 0.36 mm. The size is compact enough to be placed in cap part of capsule to avoid overlapping and coupling losses with surrounding circuitry. Initially the ingestible antenna along with circuitry and capsule were designed and placed inside homogenous stomach box using Ansys HFSS tool for the analysis, later the capsule system is placed inside different parts of the realistic virtual human phantom model and the comparative analysis is presented using the reflection coefficient curves and specific absorption rate (SAR). The SAR analysis is carried as per the Federal Communications Commission (FCC) over 1 g volume tissue, and it is 0.74 W/Kg for the proposed ingestible antenna for input power of 1 mW. The proposed antenna maintained its operational band with good impedance matching and S11 below − 10 dB making to robust and insensitive towards the variation of tissues dielectric properties in gastrointestinal tract (GI). The presented coupling strength analysis from endoscopy antenna to outside antenna proved its ability to communicate. The link budget analysis for the GI tissues proved that the margin between the actual link and the required strength is good for up to 5 m distance between the Tx and Rx antennas. Moreover, the fabricated model is measured under minced pork condition and compared analysis between the simulated and measured showed that proposed antenna-maintained impedance matching below − 10 dB in the operational band from almost 2.7 to 3.8 GHz showing significant agreement for without circuit case. The overall measured bandwidth is 1100 MHz, at operating frequency 3.3 GHz the measured return loss is − 18 dB.